Birch tree named `Fargo`

ABSTRACT

A new and distinct cultivar of birch tree plant named `Fargo`, characterized by its distinctive narrow columnar growth habit, branching angles which average about 40° with the trunk; dark-green leaf color; bark color changes as tree matures; slightly exfoliating bark when mature; leaf retention into very late autumn; winter hardiness; high tolerance to wind; adaption to high-pH soil; above average resistance to the insect leaf miner; and high tolerance to drought and heat.

The present invention comprises a new and distinct cultivar of birchtree, botanically known as Betula platyphylla, and hereinafter referredto by the cultivar name `Fargo`.

BACKGROUND OF THE INVENTION

`Fargo` is a product of a planned breeding program which had theobjective of creating a new cultivar of birch tree having improvedhorticultural characteristics, such as unique growth habit, enhancedhardiness, greener leaves, better adaptation to alkaline soil, andimproved resistance/tolerance to insects. `Fargo` was originated from anopen-pollinated cross in a birch selection/breeding program at NorthDakota State University, Fargo, ND, U.S.A. in 1986. The female parentwas Betula platyphylla grown in North Dakota State University'sArboretum near Absaraka, ND. The arboretum was established by Dale E.Herman. The seeds were collected by Arthur A. Boe from a Betulaplatyphylla tree and sown in the Fall of 1986. The male parent of`Fargo`is unknown. `Fargo` was first noticed with upright growth habitfrom the progeny of the stated open-pollinated cross by Dale E. Hermanin the Summer of 1989 in a field research plot in the West Campus ofNorth Dakota State University, Fargo, ND. `Fargo` was continuouslyobserved by Arthur A. Boe until December 1992, and then by Zong-MingCheng until the present. The first act of asexual reproduction of`Fargo` was accomplished by grafting to B. platyphylla rootsocks, thenby micropropagation or tissue culture propagation by the inventors fromthe initial selection beginning in the Summer of 1992 in a controlledenvironment in Loftsgard Hall, Room 204, North Dakota State University,Fargo, ND. Horticultural examination of selected units has demonstratedthat the combination of characteristics as herein disclosed for `Fargo`are firmly fixed and are retained through successive generations ofasexual reproduction. `Fargo` has been observed in Fargo, ND; Mandan,ND; St. Paul, MN; and Saskatchewan, Canada since 1993 andcharacteristics have been stably maintained. `Fargo` has not beenevaluated under all possible environmental conditions. The phenotype mayvary with variations in environment such as temperature, soil pH,rainfall, light intensity and day length, without a change in thegenotype of the plant. The following observations, measurements andcomparisons describe the plants grown in West Campus, North Dakota StateUniversity under natural field conditions which approximate thosegenerally used in commercial practice.

BRIEF SUMMARY OF THE INVENTION

The following traits have been repeatedly observed and are determined tobe basic characteristics of `Fargo`which in combination distinguish thisbirch tree as a new and distinct cultivar.

1. Distinctive narrow columnar growth habit with branching anglesaverage about 40°.

2. Dark green color of leaves (R.H.S 139A).

3. Bark colors change as the tree matures. The 3-year-old bark isgrayish orange (R.H.S 165A), 6-year-old bark orange-white (R.H.S 159B),and mature trunk yellow-white (R.H.S 158C).

4. Slightly exfoliating bark when mature.

5. Leaves are retained on the tree very late in autumn, i.e., until theend of October in Fargo, ND.

6. Very winter-hardy (tolerate -39°C., wind chill -50°C. to -70°C.).

7. High tolerance to wind (no damage to wind up to 110 kilometers perhour).

8. Adaption to high-pH soil (pH 8.0).

9. Tolerates drought and heat.

10. Above average resistance to leaf miner.

Of the many commercial birch trees known to the applicants, the mostsimilar in comparison to `Fargo` is Betula populifolia `Whitespire`. Incomparison to `Whitespire`, `Fargo` has a more columnar growth habit.`Whitespire` has pyramidal growth habit with lateral branches that havea wider angle with the trunk than `Fargo`.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying color photographs show typical characteristics of`Fargo`, with the colors being as true as possible with illustrations ofthis type.

Sheet 1 is a side view of a specimen of `Fargo` showing the columnargrowth habit.

Sheet 2 shows the exfoliating bark.

Sheet 3 is a close-up of the male and female catkins.

DETAILED BOTANICAL DESCRIPTION

In the following description, color references are made to The R.H.S.(R.H.S) Colour Chart. The color values were determined between 10:00a.m. and 2:00 p.m. in the Summer of 1995 under natural light at WestCampus of North Dakota State University, Fargo, ND.

Classification:

Botanical.--Betula platyphylla.

Commercial.--`Fargo`.

Parentage:

Origin.--Plant grown in North Dakota State University Arboretum.

Parentage.--Seed parent: Betula platyphylla. Pollen parent: unknown.

Tree:

Trunk.--Multiple stem: Single-trunked tree. Size: Maximum diameter atage 10 is approximately 9.7 cm. Bark: Yellow-white (R.H.S 158C.),exfoliate slightly when mature. Thorns and spines: None.

Branches.--Angle of attachment: Average 39.5° based on measurement of 20branches. Spacing: The crown has a maximum diameter of approximately 2.5meters. Bark: Color changes with age, 3-year-old stem bark isgrayish-orange (R.H.S 165S) and color of 6-year-old stem bark isorange-white (R.H.S 159B).

Height.--9.0-9.5 meters at 10 years of age.

Growth habit or Form.--Columnar, upright. Growth rate.--About 1-1.5meters per year, depending on summer temperature and water availability.

Foliage.--Size of leaf: Length: 4-7 cm (average 5.7 cm). Width: 4.5-5.8cm (average 5.2 cm). Shape of Leaf: Margin: Simple, alternate,ovate-cordate, with a rounded base, acuminate apices and serrate margins(about 5 serrations/cm).Texture: Smooth. Ribs and veins: 6-7 vein pairsper leaf. Pubescence distribution: Insignificant presence ence ofpubescences. Color: Upper side: Dark green (R.H.S 139A). Petiole:1.3-1.8 cm long, averaged 1.5 cm. Buds: intricate, pointed.

Catkins:

Staminate.--Shape: Pendulous, cylindrical. Size: 4-8 cm long, 0.5-1.0 cmwide (average 0.8 cm).

Pistillate.--Shape: Cylindrical. Size: 3.0-4.5 cm long (average 3.9 cm),0.5-0.9 cm wide (average 0.7 cm).

Timing of appearance of staminate and pistillate catkins.--Male catkinsdevelop during the summer and autumn and remain hanging in the treethrough the winter; the female catkins appear from the leaf axils inspring (March-April in Fargo, ND).

Timing of anthesis.--May 1-15 in Fargo, depending on springtemperatures.

Shape.--Winged nutlet.

Insect and disease resistance: Above-average resistance to leaf miner(Fenusa pusilla) as compared with about 200 other trees in the researchplot in Fargo, ND.

OTHER SIGNIFICANT CHARCTERISTICS.

1. Fast-growing 1-1.5 meters per year.

2. About 10% of the foliage is retained in tree throughout the winter.

What is claimed is:
 1. A new and distinct cultivar of birch tree plantnamed `Fargo`, as illustrated and described.